Spectral, catalytic, and antifungal studies of ruthenium(II) chalcone complexes

Article abstract of DOI:10.1080/00958971003728304

Reactions of [RuHCl(CO)(B)(EPh₃)₂] (B = EPh₃ or Py; E = P or As) and chalcones in benzene with equal molar ratio led to the formation of new complexes of the type [RuCl(CO)(EPh₃)(B)(L^1-4)] (B = PPh₃, AsPh₃ or Py; E = P or As; L = chalcone). The new complexes have been characterized by analytical and spectroscopic (IR-, electronic, ¹H-, ³¹P-, and ¹³C-NMR) data. Based on these data, an octahedral structure has been assigned for all the complexes. The chalcones are monobasic bidentate (O,O) donors and coordinate to ruthenium via phenolic and carbonyl oxygen. The new complexes exhibit efficient catalytic activity for the transfer hydrogenation of carbonyl compounds. Antifungal properties of the ligands and their complexes have been examined and compared with standard Bavistin.

Full text of DOI:10.1080/00958971003728304

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Spectral, catalytic, and antifungal
studies of ruthenium(II) chalcone
complexes
M. Muthukumar a & P. Viswanathamurthi a
a Department of Chemistry , Periyar University , Salem 636011,
Tamil Nadu, India
Published online: 25 Mar 2010.
To cite this article: M. Muthukumar & P. Viswanathamurthi (2010) Spectral, catalytic, and
antifungal studies of ruthenium(II) chalcone complexes, Journal of Coordination Chemistry, 63:7,
1263-1272, DOI: 10.1080/00958971003728304
To link to this article: http://dx.doi.org/10.1080/00958971003728304
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Journal of Coordination Chemistry
Vol. 63, No. 7, 10 April 2010, 1263–1272
Spectral, catalytic, and antifungal studies of ruthenium(II)
chalcone complexes
M. MUTHUKUMAR and P. VISWANATHAMURTHI*
Department of Chemistry, Periyar University, Salem 636011, Tamil Nadu, India
(Received 4 August 2009; in final form 11 November 2009)
Reactions of [RuHCl(CO)(B)(EPh3)2] (B ¼ EPh3 or Py; E ¼ P or As) and chalcones in benzene
with equal molar ratio led to the formation of new complexes of the type
[RuCl(CO)(EPh3)(B)(L1ꢀ4)] (B ¼ PPh3, AsPh3 or Py; E ¼ P or As; L ¼ chalcone). The new
complexes have been characterized by analytical and spectroscopic (IR-, electronic, 1H-, 31P-,
and 13C-NMR) data. Based on these data, an octahedral structure has been assigned for
all the complexes. The chalcones are monobasic bidentate (O,O) donors and coordinate to
ruthenium via phenolic and carbonyl oxygen. The new complexes exhibit efficient catalytic
activity for the transfer hydrogenation of carbonyl compounds. Antifungal properties of the
ligands and their complexes have been examined and compared with standard Bavistin.
Keywords: Ruthenium(II) chalcone complexes; Spectroscopic characterization; Catalytic
transfer hydrogenation; Antifungal study
1. Introduction
Coordination complexes of ruthenium have versatile applications [1–5]. Among the
different metal-catalyzed hydrogenation reactions, ruthenium-based catalytic systems
are effective in the transfer hydrogenation of ketones [6–9]. In view of the low cost of
reducing agent and its operational simplicity, the ruthenium-catalyzed hydrogenation,
either with isopropyl alcohol or with a formic acid/triethylamine mixture as a hydride
source, has emerged as an attractive alternative to asymmetric hydrogenation with
H2 [10]. Hence, the synthesis of new ruthenium complexes with different types of
ligands as catalysts for transfer hydrogenation is of particular interest.
The preparation of a new ligand is perhaps the most important step in the
development of metal complexes with unique properties and novel reactivity.
Chalcones, an important class of compounds that are widely distributed in nature,
have displayed an impressive array of pharmacological activities including antimalarial
and antileishmanial [11], as well as antimicrobial, anti-inflammatory, and antiviral
effects [12]. Several chalcones are intensively studied, modified, and synthesized in order
to develop more potential biological activities [13–16].
*Corresponding author. Email: viswanathamurthi@rediffmail.com
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2010 Taylor & Francis
DOI: 10.1080/00958971003728304

1264
M. Muthukumar and P. Viswanathamurthi
H C
3
O
O
OH
C O
HC
CHR
Ligand
R
1
L
4-(CH )C H
3 6 4
2
L
4-(OCH )C H
3 6 4
L3
4-(Cl)C H
6 4
4
L
3,4-(OCH ) C H
3 2 6 3
Figure 1. Structure of chalcone.
In this article, we describe the synthesis, catalytic, and antifungal studies of a series of
ruthenium(II) chalcone complexes. The chalcone used in this study was derived from
dehydroacetic acid (DHA, 3-acetyl-4-hydroxy-6-methyl-2-oxo-2H-pyran). The general
structure of the chalcone ligands used in this study is given in figure 1.
2. Experimental
2.1. Materials and methods
All reagents were chemically pure and of AR grade. The solvents were purified and
dried according to the standard procedures [17]. RuCl3 Á 3H2O was purchased from
Loba Chemie Pvt. Ltd. and used without purification. Analyses of carbon, hydrogen,
and oxygen were performed in a Carlo Erba 1108 analyzer at Central Drug Research
Institute (CDRI), Lucknow, India. FT-IR spectra were recorded in KBr pellets with a
Nicolet FT-IR spectrophotometer ranging from 400 to 4000 cmꢀ1. Electronic spectra of
the complexes were recorded on a Shimadzu UV-Vis 1650 PC spectrophotometer
ranging 200–800 nm using CH2Cl2 as solvent. NMR spectra (1H, 31P, and 13C) were
recorded in Jeol GSX-500 instrument in CDCl3. The 1H- and 13C-NMR spectra
were obtained using TMS as an internal standard. 31P-NMR spectra of the complexes
were obtained using orthophosphoric acid as reference. The catalytic yields were
determined using ACME 6000 series gas chromatography instrument equipped with a
flame ionization detector (FID) using a DP-5 column of 30 m length, 0.53 mm diameter,
and 5.00 mm film thickness. Melting points were recorded on a Technico micro heating
table and are uncorrected. The starting complexes [RuHCl(CO)(PPh3)3] [18],
[RuHCl(CO)(AsPh3)3] [19], [RuHCl(CO)(Py)(PPh3)2] [20], and chalcone ligands [21]
were prepared according to the literature methods.
2.2. Synthesis of new ruthenium(II) chalcone complexes
All complexes were prepared by the following procedure. An appropriate chalcone
(0.0249–0.0411 g; 0.1 mmol) was added in 1 : 1 molar ratio to a solution of

Ruthenium(II) chalcone complexes
1265
[RuHCl(CO)(EPh3)2(B)] (E ¼ P or As; B ¼ PPh3, AsPh3 or Py) (0.1 g; 0.1 mmol) in
benzene (20 cm3). The mixture was heated under reflux for 6 h in a water bath. The
reaction mixture gradually changed to a deep color during heating. After the reaction
time, the contents were concentrated to around 3 cm3 by removing the solvent under
reduced pressure. The contents are cooled and then the product was separated by the
addition of 10 cm3 of petroleum ether (60–80ꢁC). The product was recrystallized from
the CH2Cl2/petroleum ether mixture and dried under vacuum over fused calcium
chloride. The purity of the complexes was checked by thin-layer chromatography (TLC;
yield 76–89%).
2.3. Procedure for catalytic transfer hydrogenation of carbonyl compounds
Catalytic transfer hydrogenation was studied using [RuCl(CO)(AsPh3)2(L4)],
[RuCl(CO)(PPh3)2(L4)], and [RuCl(CO)(Py)(PPh3)(L4)] as catalysts, carbonyl com-
pounds as substrate, and KOH as promoter at 1 : 300 : 2.5 molar ratios, respectively, by
the following procedure. A mixture containing carbonyl compounds (3.75 mmol),
ruthenium complex (0.0125 mmol), and KOH (0.03 mmol) in 10 cm3 of isopropyl
alcohol was reacted under reflux in a water bath for 2 h. After the completion of
reaction, the catalyst was removed from the reaction mixture by the addition of diethyl
ether followed by filtration and subsequent neutralization with 1 mol HCl. The ether
layer was filtered through a short path of silica gel by column chromatography. The
filtrate was concentrated to ꢂ1 cm3 and subjected to GC analysis, and the hydrogenated
product was identified and determined with the authentic samples.
2.4. Procedure for antifungal activities
Some of the ligands and their ruthenium complexes were tested for in vitro growth
inhibitory activity against pathogenic fungi, Aspergillus niger and Mucor sp. cultured on
sabour dextrose agar medium and incubated at 30ꢁC for 72 h. The solvent (DMSO) was
used as a control in a similar manner to the prepared solutions of the compounds.
Inhibition of fungal growth, expressed in percentage terms, was determined from the
growth on test plates compared to the respective control plates, as given by the
following equation:
100ðC ꢀ T Þ
Inhibitionð%Þ ¼
C
where C and T denote the diameter of fungal growth on the control plate and the test
plate, respectively.
3. Results and discussion
Ruthenium(II) complexes [RuCl(CO)(EPh3)(B)(L1–4)] were synthesized in good yield
from the reaction of [RuHCl(CO)(EPh3)2(B)] with the chalcone ligands in dry benzene
in equal molar ratio (scheme 1). In all these reactions, the chalcones are monobasic

1266
M. Muthukumar and P. Viswanathamurthi
H C
3
O
O
OH
[RuHCl(CO)(B)(EPh ) ]
+
3 2
C O
HC
CHR
Benzene/
Reflux 6 h
H C
3
EPh
3
O
O
Cl
Ru
O
C O
CHR
CO
HC
B
(E = P or As; B = PPh , AsPh or Py; R = 4-(CH )C H , 4-(OCH )C H , 4-(Cl)C H or 3,4-(OCH ) C H )
3
3
3
6
4
3
6
4
6
4
3 2 6 3
Scheme 1. Formation of ruthenium(II) chalcone complexes.
bidentate chelating ligands, replacing a triphenylphosphine/arsine and a hydride from
the starting complexes.
The complexes are stable in air at room temperature, reddish brown in color,
non-hygroscopic, and highly soluble in common organic solvents such as dichlor-
omethane, acetonitrile, chloroform, benzene, and DMSO. The analytical data given in
table 1 are in good agreement with the general molecular formulas proposed for these
complexes.
3.1. Infrared spectroscopic analysis
Important IR absorption frequencies of the ligands and their metal complexes along
with their assignments are provided in the ‘‘Supplementary material’’. The free chalcone
ligands showed a strong ꢀC¼O band at 1628–1622 cmꢀ1, which shifts to higher
wavenumber 1659–1634 cmꢀ1 in the ruthenium complexes indicating coordination
through carbonyl oxygen [22]. A strong phenolic ꢀC–O band at 1323–1307 cmꢀ1 in the
free chalcone shifts to 1360–1339 cmꢀ1 in the complexes [22]. This is further supported
by the disappearance of the broad ꢀOH band at 3450–3350 cmꢀ1 in the complexes,
indicating the deprotonation of the phenolic proton prior to coordination to ruthenium.
Bands at 1708–1704 cmꢀ1 for the ligands are due to the lactone carbonyl group and
remain unchanged after complexation, indicating that they do not participate in bond
formation with ruthenium. Absorption due to ꢀC–C of the free ligands appeared as a
separate band around 1600 cmꢀ1, but could not be identified in the spectra of the
ruthenium complexes because of their merging with ꢀC¼O [23]. A strong band at
1958–1941 cmꢀ1 and a medium intensity band at 1028–1024 cmꢀ1 indicate the presence
of carbon monoxide [24] and nitrogen base [25], respectively. The other bands due to

Ruthenium(II) chalcone complexes
1267
Table 1. Analytical data of free ligands and their ruthenium(II) chalcone complexes.
Calculated (found) (%)
Melting
Yield (%) point (ꢁC)
Compound
Formula
C16H14O4
C16H14O5
C15H11O4Cl
C17H16O6
C53H43O5ClP2Ru
C53H43O6ClP2Ru
C52H40O5Cl2P2Ru
C54H45O7ClP2Ru
C
H
O
L1
55
58
61
64
56
64
67
71
73
69
63
79
56
65
68
70
125
138
140
162
145
158
141
135
123
180
192
184
138
120
152
128
71.10 (71.08) 5.22 (5.18) 23.67 (23.37)
67.12 (67.14) 4.92 (4.85) 27.94 (27.78)
61.97 (61.89) 3.81 (3.83) 22.01 (22.05)
64.55 (64.53) 5.09 (5.15) 30.34 (30.29)
66.42 (66.32) 4.52 (4.53) 8.35 (8.27)
65.33 (65.38) 4.45 (4.50) 9.85 (9.80)
63.80 (63.72) 4.12 (4.15) 8.17 (8.10)
64.57 (64.62) 4.52 (4.52) 11.15 (11.10)
60.84 (60.86) 4.14 (4.13) 7.64 (7.60)
59.92 (60.02) 4.08 (4.08) 9.04 (9.12)
58.55 (58.49) 3.78 (3.68) 7.49 (7.52)
59.38 (59.40) 4.15 (4.19) 10.25 (10.21)
61.98 (61.94) 4.29 (4.18) 10.31 (10.29)
60.72 (60.63) 4.20 (4.16) 12.13 (12.12)
58.87 (58.86) 3.80 (3.75) 10.05 (10.00)
59.96 (60.01) 4.29 (4.30) 13.63 (13.60)
L2
L3
L4
[RuCl(CO)(PPh3)2(L1)]
[RuCl(CO)(PPh3)2(L2)]
[RuCl(CO)(PPh3)2(L3)]
[RuCl(CO)(PPh3)2(L4)]
[RuCl(CO)(AsPh3)2(L1)] C53H43O5ClAs2Ru
[RuCl(CO)(AsPh3)2(L2)] C53H43O6ClAs2Ru
[RuCl(CO)(AsPh3)2(L3)] C52H40O5Cl2As2Ru
[RuCl(CO)(AsPh3)2(L4)] C54H45O7ClAs2Ru
[RuCl(CO)(Py)(PPh3)(L1)] C40H33O5ClNPRu
[RuCl(CO)(Py)(PPh3)(L2)] C40H33O6ClNPRu
[RuCl(CO)(Py)(PPh3)(L3)] C39H30O5NCl2PRu
[RuCl(CO)(Py)(PPh3)(L4)] C41H35O7NClPRu
triphenylphosphine or triphenylarsine (around 1440, 1090, and 695 cmꢀ1) were also
present in the spectra of all these complexes [26]. The observed bands in the region
474–456 cmꢀ1 in the mononuclear complexes are tentatively assigned to ꢀRu–Cl [27].
From the IR spectral data, the chalcones are monobasic bidentate ligands coordinating
through the deprotonated phenolic and the carbonyl oxygens.
3.2. Electronic spectroscopic analysis
All the chalcone ruthenium complexes are diamagnetic, indicating ruthenium in the 2þ
oxidation state. The electronic spectra of all the complexes in dichloromethane showed
two to four bands in the region 254–433 nm (table 2). The bands around 339–433 nm
have been assigned to charge transfer (CT) transitions based on their extinction
coefficient values (table 2) [28]. The other high-intensity bands around 296–299 and
254–256 nm are designated as n–ꢁ* and ꢁ–ꢁ* transitions, respectively, for electrons
localized on the phenolic and carbonyl groups of the chalcones. The nature of the
observed electronic spectra and the position of absorption bands are consistent with
those of other similar ruthenium(II) octahedral complexes [29].
3.3. 1H-NMR spectroscopic analysis
1H-NMR spectra of the ruthenium(II) chalcone complexes and ligands were recorded to
confirm the binding mode of chalcone to ruthenium ion. All the complexes exhibit
overlapping multiplets in the region 6.5–8.0 ppm (Supplementary material), assigned to
phenyl groups present in PPh3, AsPh3, pyridine, and chalcone [30]. The signal due to
two alkene protons at 6.6–7.1 ppm merged with the multiplets of aromatic protons [30].
Methine proton, which appeared as a singlet around 5.3 ppm in the complexes [31],

1268
M. Muthukumar and P. Viswanathamurthi
Table 2. Electronic spectroscopic data (nm) of ruthenium(II) chalcone complexes.
Complex
ꢂmax (", dm3 molꢀ1 cmꢀ1
)
Assignments
[RuCl(CO)(PPh3)2(L1)]
[RuCl(CO)(PPh3)2(L2)]
[RuCl(CO)(PPh3)2(L3)]
[RuCl(CO)(PPh3)2(L4)]
[RuCl(CO)(AsPh3)2(L1)]
[RuCl(CO)(AsPh3)2(L2)]
[RuCl(CO)(AsPh3)2(L3)]
[RuCl(CO)(AsPh3)2(L4)]
[RuCl(CO)(Py)(PPh3)(L1)]
[RuCl(CO)(Py)(PPh3)(L2)]
[RuCl(CO)(Py)(PPh3)(L3)]
[RuCl(CO)(Py)(PPh3)(L4)]
406 (6574), 368 (7986), 297 (19,130), 254 (23,215)
406 (6574), 369 (8543), 299 (20,430), 254 (23,215)
392 (6285), 369 (8543), 297 (19,130), 256 (24,532)
433 (6963), 406 (7543), 369 (8543), 297 (19,130)
353 (7196), 296 (18,128), 256 (24,532)
395 (6318), 371 (9108), 297 (19,130), 254 (23,215)
339 (6596), 296 (18,128), 256 (24,532)
368 (7986), 256 (24,532)
364 (7254), 297 (19,130), 256 (24,532)
395 (6318), 369 (8543), 254 (23,215)
364 (7254), 297 (19,130), 256 (24,532)
400 (6293), 369 (8543), 297 (19,130), 256 (24,532)
n–ꢁ*, ꢁ–ꢁ*, CT
n–ꢁ*, ꢁ–ꢁ*, CT
n–ꢁ*, ꢁ–ꢁ*, CT
n–ꢁ*, ꢁ–ꢁ*, CT
n–ꢁ*, ꢁ–ꢁ*, CT
n–ꢁ*, ꢁ–ꢁ*, CT
n–ꢁ*, ꢁ–ꢁ*, CT
n–ꢁ*, ꢁ–ꢁ*, CT
n–ꢁ*, ꢁ–ꢁ*, CT
n–ꢁ*, ꢁ–ꢁ*, CT
n–ꢁ*, ꢁ–ꢁ*, CT
n–ꢁ*, ꢁ–ꢁ*, CT
shifted upfield from the spectra of the free ligands. The absence of resonance for OH in
the complexes indicates the deprotonation of the phenol on complexation. All the
complexes showed a sharp peak at 2.14–2.17 ppm due to the methyl group attached to
the pyrone ring. The peak at 1.42–1.43 ppm is assigned to aldehyde methyl and methoxy
proton that appeared as a singlet at 3.62–3.83 ppm.
3.4. 31P-NMR spectroscopic analysis
31P-NMR spectra confirm the presence of triphenylphosphine in the new complexes
(Supplementary material). For complexes containing two triphenylphosphines, a sharp
singlet at 21.65–27.99 ppm indicates magnetically equivalent trans phosphorus [22]. The
spectrum of all other complexes exhibited a singlet at 20.82–20.86 ppm corresponding to
the presence of triphenylphosphine trans to heterocyclic nitrogen [30].
3.5. 13C-NMR spectroscopic analysis
The 13C-NMR spectra (Supplementary material) exhibit
a
resonance at
185.39–192.86 ppm assigned to the metal coordinated –C¼O. The signal for the metal
coordinated –C–O appeared at 179.98–181.58 ppm [32]. A signal for carbon monoxide
carbon was at 206.68–209.53 ppm in all the complexes. Carbons attached with the methyl
group and the lactone carbonyl in the pyrone ring are singlets at 159.98–162.93 and
153.88–158.89 ppm, respectively [33]. Multiplets around 110.66–138.32 ppm have been
assigned to the aromatic carbons. Alkene carbons at 115.45–130.58 ppm merged with the
aromatic carbons. Sharp singlets at 19.84–19.97 ppm are assigned to methyl carbon
attached to the pyrone ring and 16.25 ppm region is assigned to the aldehyde methyl
group. Sharp singlet at 55.32–55.99 ppm is assigned to methoxy carbon. Based on the
analytical and spectroscopic (IR-, electronic, 1H-, 31P-, and 13C-NMR) data, an
octahedral structure (figure 2) is proposed for the ruthenium(II) chalcone complexes.
3.6. Catalytic transfer hydrogenation of carbonyl compounds
Three ruthenium(II) chalcone complexes were studied for the catalytic transfer
hydrogenation of various types of aldehydes and ketones in the presence of isopropyl

Ruthenium(II) chalcone complexes
1269
H C
3
EPh
3
O
O
O
C O
CHR
Cl
Ru
B
CO
HC
(E = P or As; B = PPh , AsPh or Py; R = 4-(CH )C H , 4-(OCH )C H , 4-(Cl)C H or 3,4-(OCH ) C H )
3
3
3
6
4
3
6
4
6
4
3 2 6 3
Figure 2. Proposed structure of new ruthenium(II) chalcone complexes.
Table 3. Catalytic transfer hydrogenation of carbonyl compounds by ruthenium(II) chalcone complexesa
with isopropyl alcohol.b
Conversion
for 1 (%)c
Conversion
for 2 (%)c
Conversion
for 3 (%)c
Substrate
Product
C6H5CH2OH
p-MeC6H4CH2OH
C10H7CH2OH
p-MeOC6H4CH2OH
p-NO2C6H4CH2OH
p-ClC9H4CH2OH
C6H11OH
C6H5CH(OH)Me
Ph2CHOH
Me2CHCH2CH(OH)Me
C6H5CHO
p-MeC6H4CHO
C10H7CHO
p-MeOC6H4CHO
p-NO2C6H4CHO
p-ClC6H4CHO
94
91
82
87
76
79
99
72
78
58
92
86
80
83
72
78
99
70
75
55
87
88
77
85
74
74
96
69
78
57
C6H10O
C6H5C(O)Me
Ph2C(O)
Me2CHCH2C(O)Me
a1 – [RuCl(CO)(AsPh3)2(L4)]; 2 – [RuCl(CO)(PPh3)2(L4)]; and 3 – [RuCl(CO)(Py)(PPh3)(L4)].
bConditions: reactions were carried out heated to reflux using 3.75 mmol of ketone (10 cm3 isopropyl alcohol);
catalyst : ketone : KOH ratio ¼ 1 : 300 : 2.5.
cYield of product was determined using a ACME 6000 series GC-FID with a DP-5 column of 30 m length, 0.53 mm diameter,
and 5.00 mm film thickness and by comparing with the authentic samples.
alcohol and KOH. The catalysts performed efficiently for the conversion of aldehydes
and ketones to alcohols (table 3). Benzaldehyde was converted into benzyl alcohol in
87–94% yield; for 4-methyl benzaldehyde and 4-methoxy benzaldehyde, the conver-
sions were 86–91% and 83–87%, respectively. Reduction of 4-chlorobenzaldehyde and
4-nitrobenzaldehyde to the corresponding alcohol occurred in 74–79% and 69–76%
yields, respectively. The catalyst performed moderately for the reduction of
naphthaldehyde. These catalysts show good activity for the transfer hydrogenation of
aliphatic and aromatic ketones to the corresponding alcohols; cyclohexanone,
acetophenone, and benzophenone were converted to the corresponding alcohols in
96–99%, 69–72%, and 75–78% yields, respectively, after 2 h reactions. For iso-butyl
methyl ketone, the efficiency of the catalyst was moderate (55–58%). No transfer
hydrogenation takes place in the absence of base. Although no studies have been
carried out to determine the mechanism for these particular catalytic processes, it is
generally assumed that the base facilitates the formation of ruthenium alkoxide by
abstracting the proton from the alcohol and subsequently alkoxide undergoes
ꢃ-elimination to give ruthenium hydride, which is an active species in the transfer
hydrogenation reaction (scheme 2) [7, 34–36]. The workup process is very simple for this

1270
M. Muthukumar and P. Viswanathamurthi
B
O
O
Cl
H CO
3
O
C
O
O
Ru
O
R
CO
EPh
3
i-PrOH +
KOH
–KCl, H O
2
B
O
O
O
R1
OH
H
Ru
CH
CO
EPh
3
O
R
2
OH
H
H
R
1
B
B
O
O
H
O
O
O
R
2
Ru
Ru
EPh
CO
CO
EPh
3
3
R
1
B
H
O
O
R
2
O
R
1
Ru
O
CO
EPh
R
3
2
(E = P or As; B = PPh3, AsPh3 or Py)
Scheme 2. Mechanism of catalytic transfer hydrogenation reactions.
catalytic system as the catalyst is stable in all organic solvents and can be easily
recovered.
3.7. Antifungal activity
The in vitro antifungal screening against A. niger and Mucor species for the ligands and
ruthenium(II) chalcone complexes have been carried out by disc diffusion method [37].
The ruthenium complexes (table 4) are more toxic than their parent ligands against the
same microorganisms under the identical experimental conditions. The increase in the
antifungal activity of the metal chelates may be due to Tweedy’s chelation theory
[38, 39]. Toxicity of the compounds increases with an increase in concentration. Though
the complexes possess activity, they do not reach the effectiveness of the standard drug
Bavistin. The variation in the effectiveness of the different compounds against different
organisms depends either on the impermeability of the cells of the microbes or
differences in ribosomes of microbial cells.

Ruthenium(II) chalcone complexes
1271
Table 4. Fungicidal activity data for selected ligands and their ruthenium(II) chalcone complexes.
Diameter of inhibition zone (mm)
A. niger
Mucor sp.
Compound
50 ppm
100 ppm
50 ppm
100 ppm
L1
7
18
16
15
10
15
20
22
38
11
34
32
33
13
28
37
38
56
8
16
15
17
7
18
26
24
42
13
32
30
35
11
34
31
35
53
[RuCl(CO)(PPh3)2(L1)]
[RuCl(CO)(AsPh3)2(L1)]
[RuCl(CO)(Py)(PPh3)(L1)]
L2
[RuCl(CO)(PPh3)2(L2)]
[RuCl(CO)(AsPh3)2(L2)]
[RuCl(CO)(Py)(PPh3)(L2)]
Bavistin
4. Conclusions
Several new ruthenium(II) chalcone complexes were synthesized from the derivatives of
dehydroacetic acid and 4-substituted benzaldehyde. An octahedral structure has been
proposed for the complexes which showed efficient catalytic activity for the transfer
hydrogenation of aldehydes and ketones with high conversions. Though some
ruthenium complexes have been found in recent literature [40–45], the ruthenium(II)
chalcone complexes have been rarely seen as catalysts for this kind of transfer
hydrogenation reaction. In our system, labile triphenylphosphine makes these
complexes catalytically active and the activity may be tuned by altering the substituents
in the chalcone. The complexes exhibited a considerable antibacterial activity.
Acknowledgments
The authors express their sincere thanks to the Council of Scientific and Industrial
Research (CSIR), New Delhi, (grant no. 01(2065)/06/EMR-II) for providing financial
support. M. Muthukumar thanks CSIR for awarding Senior Research Fellowship.
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